Muscular tension as an index of effort : the effect of glare and other disturbances in visual work.

In utilising muscular action potentials as an index of effort, we have used apparatus and experimental designs which permit: (1) continuous recording and totalization of electrical activity during each period of work, (2) reasonable freedom of movement and normal posture of the worker in a sedentary task, (3) the use of untrained subjects and only one or two observation periods per subject, thus making feasible a wide sampling of subjects, and (4) simultaneous recording of potentials from four areas of the body.